Architectural joint systems commonly are installed to bridge over open space provided between two adjacent architectural structures which are expected to have relative movement, resulting from normal expansion and contraction, seismic activity or otherwise. One frequently employed type of architectural joint system incorporates a cover plate which extends over the open space and has side margins supported by the relatively movable structures on either side thereof. A centering mechanism is provided for maintaining the cover plate in centered relation to the open space, as the structures move toward and away from each other. Typically, such centering mechanisms involve the provision of guide rail means on each of the structures defining guide grooves or channels which extend along the adjacent edges of the structures. A plurality of centering bars are pivotally connected to the cover plate at various points along its length and are provided at their opposite ends with guide elements arranged to be received in the beforementioned guide grooves. Movement of the structures toward and away from each other causes the centering bars to pivot about their center points connected to the cover plate. This results in the center plate being held in a symmetrical, centered position relative to the movable structures.
Early designs of centering mechanisms of the type described above are shown in U.S. Pat. No. 3,183,623 and U.S. Pat. No. 4,566,242. Especially advantageous forms of such centering mechanisms are shown in my copending U.S. Pat. application Ser. No. 881,493, filed May 11, 1992. The present invention is directed particularly to a novel and advantageous form of centering bar element for utilization in such mechanisms.
In centering bar devices of known design, it is common to form the main body of the bar of a length of metal strip of the desired length, on the opposite ends of which are mounted guide elements of a suitable size and shape. For some installations, the guide elements may be spheres or semi-spheres, or perhaps cylinders, formed of plastic. The guide elements may also be formed of metal, depending on the load requirements. Conventionally, the guide elements are fastened to the flat metal bars by mounting pins or the like, which are fixed in the flat bar and extend upward into the guide element. In the case of the beforementioned U.S. Pat. No. 4,566,242, the metal bar is embedded into plastic guide elements. For attachment of the centering bar to the cover plate, the metal bar may be provided with a threaded center opening, for example, or a threaded sleeve or the like may be attached to the center of the bar.
In any of a number of its existing forms, the centering bar constitutes a relatively labor intensive, costly component, which inherently has significant weaknesses, especially in the attachment of guide elements to the outer ends of the main metal bar.
In accordance with the present invention, a novel and significantly improved centering bar device is provided, which is not only significantly less costly to manufacture, but is at the same time greatly improved in performance. Specifically, the centering bar is designed and constructed as a single, integral unit, advantageously molded of engineering plastic materials, or cast of metal. Importantly, the guide elements, mounted at the opposite ends of the centering bars, are integral portions of the bar as a whole, greatly increasing the strength of the unit at the critical outer end region. In the center of the unit, there is provided an integral base section, which extends at least in one direction. Usually downward, and preferably upward as well, from the radially extending arms which form the main body of the bar. Strengthening means, typically in the form of tapered webs or the like, extend from the base portion outwardly along the arm portions.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment of the invention and the accompanying drawings.